Identifier of an MCI device. This identifier or alias is assigned when the
device is opened.

lpszFreezeFlags

Flag that identifies what to freeze. The following table lists device types
that recognize the freeze command and the flags used by each type:

digitalvideo

at rectangle

outside

overlay

at rectangle

cr

field
frame

input
output

The following table lists the flags that can be specified in the lpszFreezeFlags parameter and their meanings:

at rectangle

Specifies the region that will be frozen. For video-overlay devices, this
region will have video acquisition disabled. For digital-video devices, the pixels
within the rectangle will have their lock mask bit turned on (unless the
"outside" flag is specified). The rectangle is relative to the video buffer origin
and is specified as X1 Y1 X2 Y2. The coordinates X1 Y1 specify the upper left corner of the rectangle, and the coordinates X2 Y2 specify the width and height.

field

Freezes the first field. Field is assumed by default (if neither frame nor
field is specified).

frame

Freezes the entire frame, displaying both fields.

input

Freezes the current frame of the input image, whether it is paused or running.

output

Freezes the current frame of the output from the VCR. If the VCR is playing
when freeze is issued, the current frame is frozen and the VCR is paused. If the VCR is
paused when this command is issued, the current frame is frozen. The frozen
image remains on the output device until an unfreeze command is issued. If neither "input" nor "output" is specified, "output" is
assumed.

outside

Indicates that the area outside the region specified using the "at" flag is
frozen.

lpszFlags

Can be "wait", "notify", or both. For digital-video and VCR devices, "test"
can also be specified. For more information about these flags, see The Wait, Notify, and Test Flags.

Return Values

Returns zero if successful or an error otherwise.

Remarks

When used with VCR devices, this command is intended for frame-grabbing cards.

To specify irregular acquisition regions with the "at" flag, use a series of freeze and unfreeze commands. Some video-overlay devices limit the complexity of the acquisition
region.

This command is supported only if a call to the capabilitycommand with the "can freeze" flag returns TRUE.

The following command disables video acquisition in a 100-pixel square at the
upper left corner of the video buffer: